Acceleration responsive switch



April 11, 1961 P. R. WEAVER 2,979,582

ACCELERATION RESPONSIVE SWITCH Filed May l2, 1959 48 Tllzl.

INVENTOR aafsroAfluawn? ATTORNEYS United StateSPatCrlf i AccELERA'rIoN RESPONSIVE SWITCH Preston R. Weaver, Nyack, N.Y., assignor to The W. L. MaxsonCorporation, New York, N.Y., a corporation of New York Filed May 12, 1959, Ser. No. 812,638

10 Claims. (Cl. 200e-61.45)

This invention pertains to acceleration responsive switches and particularly to integrating switches of this type which close after a given velocity is reached.

The present invention provides an acceleration switch having a cylinder and a piston therein which draw a gas through an orifice controlled by a valve for adjusting the time required for switch closure. When the orifice is reduced in size thus creating a restraint to the flow of gasfand the switch kis subjected to an acceleration whose rise time is short compared to the desired delay time, a pressure difference will exist between the bottom and top chambers inthe cylinder and atinite time'will be required for the piston to travelthrough the cylinder. The pressure on either side of the orifice and the piston willy be equal under ambient conditions, The only way a pressure difference can be attained is by accelerating the'switchy unit in sucha manner as to cause the piston to be displaced. j

One object of the present invention is to provide an acceleration switch which is readily adjustable to control the magnitude and duration of the acceleration to which it will respond.

Another object of the invention is to provide an acceleration responsive switchwhich is safe against vaccidentaloperation due to yvibration or sudden accelerations of short duration. vThis lobjective is accomplished by locking the movable contacts of the switch so that they are incapable of being operated until unlocked in response to a predetermined amount of acceleration. Y

yAnother object of the invention is to provide an acceleration responsive switch which is locked against further operation, after response to a predetermined amount of acceleration, until the switch is manually reset to condition it -for another operation. f

The above andpother objects and advantages of the invention will become apparent from the following descriptionand the drawing in which: y y j Fig. l is an elevation partly in section of one embodiment of the invention; K

Fig. 2 is a view similar to Fig. l showing the switch after it has been actuated by an acceleration; and

, Figs. 3 and 4 are detail views showing the switch contacts in the unaetuated and in the actuated positions, respectively.

`Referring to the drawing, a hermetically sealed casing l ,is provided. Within the casing is'mounted by any suitable means a fixed cylinder 12 comprising side walls 13,A top wall 14 and a bottom or end closure 15. These elements may be joined together by any suitable means such as screws 16 to form an air-tight chamber for piston 18.y The piston is integral with a shaft 19 having a portionf20 of reduced diameter and an enlarged end 21.

2 formed by ball bearings 25 and spring 26 urges piston 18 upward.

The top of the cylinder is provided with an oriiice 28 which is closed by valve 29. Valve 29 is preferably threaded and includes a slot 30 for permitting screw driver adjustment of the eifective size of the orifice. By controlling the size ofthe `orifice the damping of the movement of the piston can be adjusted over a wide range of limits.

A lever 32 having a ball bearing 33 at one end norma1- ly rides against the enlarged end 21 of the shaft. Contact between elements 33 and 21 is maintained by a spring 34 fastened at one end 35 and at the other end engaging pin 36 on lever 32. Lever 32 is pivoted at 37 and has an arm 38 adapted to engage the upper face of a bar 39 of the movable contact assembly. Lever 32 is carries a pair of movable contacts 53 having conductive portions 54. The movable contacts are adapted to x spring contacts 55 and 56 which may be provided with suitable terminals 57 and 58 from which conductors (not shown) may extend through a suitable connector plug 59.

The operation of the switch will now be explained.

When no acceleration has occurred the elements of the` switch are in the positionshown in Fig. l and after an acceleration they are in the position shown in Fig. 2. Fig. 3 shows the position of the switch contacts in Fig. l and Fig. 4 shows the position of the switch contacts Fig. 2. The displacement of piston 18 under an acceleration is controlled by the size of the orifice 28 as adjusted by valve 29 and also by the size of the spring 26 and the mass of piston 18 and shaft 19, including its ends portions 20 and 21. When an acceleration of suffcient magnitude and duration occurs in the upward direction the piston 18 moves downwardly in the cylinder and compresses the spring 26 as shown in Fig. 2. Thereupon the roller 33 of lever 32 rides oit the end 21 onto Y the shaft portion 20 of reduced diameter and thus engages the top of the enlarged end 21 to lock it against movement toward the cylinder by spring 26. Roller 33 is held in its locking position by spring 34. This movement of lever 32 will remove the shoulder 40 from j the bar 39 and permit the spring 41 to move the movable The mass yof* theshatt 19 vand piston 18, including the porv contact assembly downward into the fixed contacts 55 and 56. In executing this movement the rod 42 turns lever 43 so as to bring the arm 46 thereof into engagement with the pin 49. Thus, the switch is maintained in its closed or armed position (Fig. 2) and the acceleration sensing elements 18-21 are locked against further operation. If it is desired to reset the switch the reset plunger 48 is depressed to cause the pin 49 to move the arm 46 downward into the position shown in Fig. 1. This operation causes the end 44 of lever 43 to raise the rod 42v and thereby retract the movable contact assembly 39, etc. upwardly against spring 41 and also to move the lever arm 38 upwardly so as to disengage the ball bearing 33 from the end portion Z1 of the shaft 19. By holding the elements in this position for a sutiicient time the spring 26 is permitted to move 'the piston 18 and shaft 19 upwardly into the unarmed position illustrated in Fig. 1. The switch is then in condition for anothe;y operation.

VOne feature of the switch of this inventionisuthat it Patented Apr.`11, 1961` is impossible for the contacts to be transferred or actuated unless the piston has been displaced a predetermined distance. Another advantage of the present switch is that the effect of vibration is minimized by the spring 26, the locking means 33 and the shoulder 34. Another advantage of the invention isthat the damping of the piston by the Valve arrangement can be made very large in order to prevent motion of the piston under vibration over a wide range of frequencies, for example, 10-2000 cycles per second. Shock tests of up to 10() g with rise times of 6 to l0 milliseconds and durations from 10 to 100 milliseconds have failed to cause the switch to 'be actuated. By virtue of the damping provided by adjustable orice 2S, a considerable delay time is introduced for the operation of the switch; in other words, the acceleration is integrated over an appreciable time so that the switch closes only after a certain velOcity has been attained. The following table indicates the velocity required to close the switch with different applied accelerations for one embodiment of the invention.

Applied Acceleration Velocity to Close, FtJsec Ft./sec. A/ G 270 8. 4 1, 190 278 8. (iy 1, 192 343 10. 7 1, 046 344 10. 7 1, 101 401 12. 5 998 403 l2. 5 991 474 14. 7 900 468 14. 5 945 a relatively large mass, spring means resiliently urging said piston in one direction for retracting said shaft into said cylinder, said shaft having portions of different diameters outside said cylinder, a spring pressed lever having one end in engagement with said shaft, a switch having a fixed contact and a cooperating movable switch contact member posi-tioned to be engaged by the other end of said lever, whereby said piston and said shaft move in said cylinder oppositely to said one directionV in response to an acceleration of a given magnitude and duration.

2. An acceleration responsive switch according to claim l, wherein said cylinder has an orifice at its other end and an adjustable valve in said orifice for controlling the speed of movement of said piston in said cylinder.

3. An acceleration responsive switch according to claim 2, including means for manually resetting said lever and said movable contact member to the unoperated position.

4. An acceleration responsive switch according to claim 3, wherein said lever includes means engaging the movable contact member for latching the same against accidental closure.

5. An acceleration responsive switch as in claim 4 including means for locking said piston and shaft against retraction into said cylinder after said `piston and shaft have been actuated by an acceleration ofV said given magnitude and duration. j

6i An acceleration responsive switch comprising asubstantially air-tight cylinder, a piston in said cylinder, said cylinder having an opening at one end and said piston having a shaft extending axially from said piston through said opening and having a substantially gastight sliding t therewith, said piston and said shaft having a relatively large mass, said cylinder having an adjustable valve on one side :of said piston for controlling the speed of movement of said piston in said cylinder, a spring means in said cylinder resiliently urging said piston in one direction for retracting said shaft into said cylinder, said shaft having an intermediate portion of a diameter smaller than that of the outer end of the shaft, a spring pressed lever having one end in engagement with said shaft, a switch including fixed contacts and cooperating movable contacts positioned to be engaged by the other end of said lever, means on said other end of the lever for latching the movable contacts against movement toward the fixed contacts, means for moving said movable contacts into engagement with the fixed contacts in response to movement of said' lever against said intermediate portion of the shaft, whereby said switch is actuated in response to an acceleration.

7. An acceleration responsive switch comprising a substantially air-tight cylinder, a piston in said cylinder, said cylinder having an opening at one end and said piston having a shaft extending axially from said piston through said opening and having a substantially gas tight sliding fit therewith, said piston and said shaft having a relatively t large mass, said cylinder having an adjustable valve on one side of said piston for controlling the speed of movement of said piston in said cylinder, a spring means in said cylinder for resiliently retracting said shaft into said cylinder, said shaft having an enlarged portion at its outer end and an intermediate portion of smaller diameter, a lever,y spring means holding one end of said lever in engagement with said enlarged end of the shaft, a switch including fixed contacts and cooperating movable contacts, latching means on the other end of said lever for engaging the movable contacts and preventing their movement toward the fixed contacts, additional spring means for actuating the movable contacts when released from said latching means` by a movement of the lever in response to an acceleration of a given magnitude and duration, and resetting means for retracting the movable contacts and the lever and thereby enabling said spring means to retract said piston.

8. An acceleration response switch comprising a substantially air-tight cylinder, a piston in saidcylinder, said cylinder having an opening at one end and said piston having a shaft extending axially from said piston through said opening and having a substantially gastight sliding it therewith, said piston and said shaft having a relatively large mass, adjustable valve means for venting at a given rate the cylinder space at one end of said piston, spring means resiliently urging said piston in one direction for retracting said shaft into said cylinder, said shaft having portions of different diameters outside said cylinder, a member having one end in engagement with said shaft,

spring means for resiliently holding said member against said shaft, xed switch contacts and cooperating movable switch contacts, second spring means for closing said switch contacts in response to the relative movement of said shaft and saidmember.

9. An acceleration responsive switch as in claim 8 ncluding Vmeans for locking said piston and shaft against retraction into said cylinder after said piston and shaft have been actuated by an acceleration having .a given magnitude and duration.

10. An acceleration responsive switch comprising a substantially gas-tight cylinder, a piston in said cylinder, said cylinder having an opening at one end and said piston having a shaft extending axially from said piston through said opening and having a substantially `gas-tight sliding fit therewith, said piston and said shaft having a relativelyl largeV mass, said. cylinder having an adjustable valve on agresse one side of said piston for controlling the speed of movement of said piston in said cylinder, said shaft having an intermediate portion of a diameter smaller than that of the outer end of the shaft, a rst spring means resiliently urging said piston in one direction in said cylinder, a lever, a second spring means for holding one end of said lever in contact with said shaft, a switch including xed contacts and cooperating movable contacts, third spring means for moving said movable contacts into engagement with the fixed contacts in response to movement of said lever, latch means on said lever for restraining the movable contacts against movement toward the fixed contacts,

and means including said lever for releasing said latch means in response to a predetermined movement of said piston, whereby said third spring means actuates said movable contacts into engagement with the fixed contacts in response to an acceleration of given magnitude and duration.

References Cited in the tile of this patent UNITED STATES PATENTS 2,854,539 Ruppel Sept. 30, 1958 

